The present invention relates to semiconductor integrated circuit devices, and more particularly to a semiconductor integrated circuit device in which a measure against hot carriers and a measure against electrostatic breakdown are taken, and whose internal circuit has a MOS field effect transistor of the LDD (Lightly Doped Drain) structure, as well as a method of manufacturing the same.
In a semiconductor device, especially a microminiaturized semiconductor device, comprising metal-oxide-semiconductor field effect transistors (MOSFETs), it is proposed to employ the LDD structure for a source and a drain to the end of preventing the appearance of hot carriers. With the LDD structure, source and drain regions are each constructed of a high impurity concentration region formed away from a gate electrode (hereinbelow, expressed as `formed in offset to a gate electrode`), and of a low impurity concentration region disposed between the high impurity concentration region and the gate electrode. Owing to the LDD structure, the electric field of a drain edge in the direction of a channel is relaxed, with the result that the appearance of hot carriers is suppressed. Thus, the degradations of element characteristics attributed to the hot carriers can be restrained, to enhance reliability. In case of, for example, an N-channel MOSFET (hereinbelow, termed `NMOSFET`), the low impurity concentration region mentioned above is set at a concentration on the order of, e.g., 10.sup.13 cm.sup.-2 and, e.g., at a length of 0.2-0.4 .mu.m.
The LDD is described in P. J. Tsang et al, IEEE Transactions on Electron Devices, Vol. ED-29, No. 4 (1982), p. 590.